Hi,

Not sure I fully understand the issue. Could you please add a screenshot?

Also, the general advice is to try running Firefox in Troubleshoot Mode. Among other things, it disables themes (in case they influence your Firefox).

Looking forward to your update!

Do you use a dark theme for your toolbars,? In that case, Firefox will try to use a dark theme for some web pages.

You can flip the Settings page back to a Light theme by choosing a "Light" website appearance. See the steps in the following article: Change website appearance settings in Firefox.

But it doesn't look like that works for the pop-up History window (Library window).

If you want to change your toolbar theme to a light theme, see: Use themes to change the look of Firefox.